Computational Methods for the Construction of a Class of Noetherian Operators

This paper presents some algorithmic techniques to compute explicitly the noetherian operators associated to a class of ideals and modules over a polynomial ring. The procedures we include in this work can be easily encoded in computer algebra packages such as CoCoA and Singular

An anisotropic numerical model for thermal hydraulic analyses: application to liquid metal flow in fuel assemblies

A CFD analysis has been carried out to study the thermal–hydraulic behavior of liquid metal coolant in a fuel assembly of triangular lattice. In order to obtain fast and accurate results, the isotropic two-equation RANS approach is often used in nuclear engineering applications. A different approach is provided by Non-Linear Eddy Viscosity Models (NLEVM), which try to take into account anisotropic effects by a nonlinear formulation of the Reynolds stress tensor. This approach is very promising, as it results in a very good numerical behavior and in a potentially better fluid flow description than classical isotropic models. An Anisotropic Shear Stress Transport (ASST) model, implemented into a commercial software, has been applied in previous studies, showing very trustful results for a large variety of flows and applications. In the paper, the ASST model has been used to perform an analysis of the fluid flow inside the fuel assembly of the ALFRED lead cooled fast reactor. Then, a comparison between the results of wall-resolved conjugated heat transfer computations and the results of a decoupled analysis using a suitable thermal wall-function previously implemented into the solver has been performed and presented

MobiDB-lite 3.0: fast consensus annotation of intrinsic disorder flavors in proteins

Abstract Motivation The earlier version of MobiDB-lite is currently used in large-scale proteome annotation platforms to detect intrinsic disorder. However, new theoretical models allow for the classification of intrinsically disordered regions into subtypes from sequence features associated with specific polymeric properties or compositional bias. Results MobiDB-lite 3.0 maintains its previous speed and performance but also provides a finer classification of disorder by identifying regions with characteristics of polyolyampholytes, positive or negative polyelectrolytes, low-complexity regions or enriched in cysteine, proline or glycine or polar residues. Subregions are abundantly detected in IDRs of the human proteome. The new version of MobiDB-lite represents a new step for the proteome level analysis of protein disorder. Availability and implementation Both the MobiDB-lite 3.0 source code and a docker container are available from the GitHub repository: https://github.com/BioComputingUP/MobiDB-lit

Infinite reduction of couplings in non-renormalizable quantum field theory

I study the problem of renormalizing a non-renormalizable theory with a reduced, eventually finite, set of independent couplings. The idea is to look for special relations that express the coefficients of the irrelevant terms as unique functions of a reduced set of independent couplings lambda, such that the divergences are removed by means of field redefinitions plus renormalization constants for the lambda's. I consider non-renormalizable theories whose renormalizable subsector R is interacting and does not contain relevant parameters. The "infinite" reduction is determined by i) perturbative meromorphy around the free-field limit of R, or ii) analyticity around the interacting fixed point of R. In general, prescriptions i) and ii) mutually exclude each other. When the reduction is formulated using i), the number of independent couplings remains finite or slowly grows together with the order of the expansion. The growth is slow in the sense that a reasonably small set of parameters is sufficient to make predictions up to very high orders. Instead, in case ii) the number of couplings generically remains finite. The infinite reduction is a tool to classify the irrelevant interactions and address the problem of their physical selection.Comment: 40 pages; v2: more explanatory comments; appeared in JHE

Aziridination of alkenes promoted by iron or ruthenium complexes

Molecules containing an aziridine functional group are a versatile class of organic synthons due to the presence of a strained three member, which can be easily involved in ring-opening reactions and the aziridine functionality often show interesting pharmaceutical and/or biological behaviours. For these reasons, the scientific community is constantly interested in developing efficient procedures to introduce an aziridine moiety into organic skeletons and the one-pot reaction of an alkene double bond with a nitrene [NR] source is a powerful synthetic strategy.Herein we describe the catalytic activity of iron or ruthenium complexes in promoting the reaction stated above by stressing the potential and limits of each synthetic protocol

Iron catalysts with N-ligands for carbene transfer of diazo reagents

Transition-metal-catalyzed carbene transfer reactions, involving diazo compounds and their precursors, are powerful tools for creating new C-C bonds. Depending on the involved catalytic system, the carbene insertion can efficiently be driven towards a specific functional group for the synthesis of a wide portfolio of fine chemicals. The present report is focused on the catalytic activity of iron catalysts in promoting alkene cyclopropanations, C-H and X-H (X = N, O, S, Se, Si, Sn, Ge) functionalizations. Porphyrin, porphyrinoid and non-heme iron complexes are discussed by analyzing experimental studies and theoretical calculations performed for proposing reaction mechanisms. The catalytic activity of artificial iron biocatalysts is also briefly reported in order to underline the similarities and differences between reaction mechanisms mediated by modified biocatalysts and synthetic catalysts. This review summarizes the achievements made in this field since 2006